Black Pipe for boiler installation?

Now that I'm having a new boiler installed and all the pipes are new/clean, I see some are black pipe? This looks like gas pipe? Why? Won't they rust? It could have been on my old 1960's boiler but everything was so dirty I just thought it was dirty copper... It's black pipe leaving the boiler and black pipe for both circulating pumps (on one end only...the other end is copper), and it's black for the expansion tank too...

Just some enlightenment is all I need.

Thanks

black pipe

That is the pipe that is almost always used on heating systems. It will not rust unless you have a leak that continually adds new oxygen laden water into the system.

Thank you!